Gyrokinetic simulations of impurity, He ash and alpha particle transport and consequences on ITER transport modelling

The transport of light and heavy impurities, as well as of energetic a particles, produced by the background electrostatic plasma turbulence is investigated by means of linear and nonlinear simulations with three gyrokinetic codes, GS2, GYRO and the recently developed GKW. The basic transport mechanisms of impurities and energetic alpha particles are elucidated, in combination with a simple analytical derivation. The relevance of these theoretical results in the transport modelling of the ITER standard scenario is assessed by means of ASTRA simulations, in which the transport of minority species like alpha particles and He ash is described by means of formulae which fit the gyrokinetic results.